1. Field of the Invention
This invention relates to the industrial manufacture of new high-performance alloys, functional materials and ultrahigh-purity materials from the vapor phase, including PVD magnesium (PVD: physical vapor deposition), PVD aluminium, PVD titanium, PVD superalloys and PVD intermetallics, (sheets, bars, profiles, forgings, layers and surface films), "Thermal Barriers", VD materials (VD: Vapor Deposition) of semiconductor technology, including elementary and/or porous silicon, and of distillation for extraction (recovery) and refining, i.e. for the production of high-purity elements, such as alkali, alkaline earth and rare earth metals, to production of high-purity and ultra-high-purity (elementary or basic) metals (transition metals, such as Zr, Cr etc.) and products of "clean-room technolgy" as such, to the production of pigments, of reinforcing components, (of alloys with dispersed) carbides, nitides, borides, oxides, silicides, fullerenes, magnets, of optical and electronic products, including the products of microelectronics, to the coating of the reinforcing components of composite materials, for the surface treatment of materials as such, and to the recycling of modern lightweight and functional materials and of lubricants as well as aqueous solutions beyond the vapor phase, the products deposited from the vapor phase assuming solid massive forms and/or solid powder forms, semifinished product forms and/or near-final contour forms in the elementary and/or alloy state, in the thermodynamically metastable or stable state, whether as metal or ceramic or as semiconductor, or being packaged in liquid form or racked off as a gaseous constituent.
In industrializing the manufacture of future products from the vapor phase, relatively long distances for the conveyanve and for the intermixing (for example, during alloying) and segregating (for example, during recycling) of the relevant vapors will have to be covered in an energy-efficient way. The length of the necessary vapor conveyance flow distances is determined, on the one hand, by the size (quantity and dimension) of the initial, intermediate and resulting products and, on the other hand, on the nature and number of the methods and operative process steps of alloying, distillation and conveyance of (in) the vapor phase. However, overcoming long vapor conveyance flow distances still always tended to involve the problem of high conveying capacities Q, indeed entirely irrespective of the thermal loading capacity and chemical reactivity of the plant materials with and in relation to the corresponding vapors. See Th. Konig et al., H. C. Starck GmbH & Co KG, D38642 Goslar, German Patent DE 4214720, 11.11.1993.
In vacuum technology, a distinction must be made, as regards results, between two pumping capacities: (i) the first pumping capacity must be applied in order to generate the vacuum, the underpressure or overpressure and/or the controlled atmospheric composition in a system which is virtually closed off relative to the environment, the environment having a pressure of one atmosphere under normal conditions; (ii) the second pumping capacity to be basically distinguished is used for producing controlled (suction) flow and (suction) conveyance movements in the vacuum, in the overpressure prevailing relative to the environment and/or in corresponding atmospheres composed in a controlled manner relative to the environment and/or in corresponding atmospheres composed in a controlled manner relative to the environment, said movements being independent of the absolute pressure value of the respective atmosphere in certain regions (particular to a specific pumping system). Just as a pump can generate an air draft under normal conditions, a pump can generate and drive a vapor flow under vacuum conditions, etc., and the pumping capacity can in various ways be uncoupled from the conveying capacity and, by controlling the conveying capacity, can be coupled to this again. The pump-unspecific pumping speed S at the inlet of a given vacuum pump station for a given vacuum chamber is a mechanical propulsion force which must be delimited relative to chemical and physical conveying operations and which is intended for the forced convection of the conveying, alloying or separating and converting operations involved. It is unimportant, in this case, whether the suction effect is produced by underpressure alone or in conjunction with a carrier gas. The pressure flow is that form of propulsion force of material conveyance which corresponds to the (technical) overpressure, whereas, in a vacuum, the suction flow is this particular form. This distinction, trivial per se, has hitherto greatly underestimated importance in light of the state of vacuvum technology and material production from the vapor phase (see F. Hehmann, F. W. Hugo, F.Muller and M. Raschke, German Patent Application P 44063334, Mar. 1, 1994, made by Leybold Durferrit GmbH, Hanau).
Gaseous suction flows are used (i) in the chemical and petrochemical industry for separating processes for the selection, for example of (for example, organic) solvents in waste air, in which the speed-determining step of diffusion through the diaphragm is controlled according to Fick's law of diffusion. Gaseous suction flows are also used (ii) in chemical vapor deposition processes (CVD), in which a chemical surface reaction and the amount of surface involved determine and limit the productivity of the CVD coating process. In the simplest form, this reaction reads as follows (cf. D. S. Rickerby and A. Matthews, Advanced Surface Coatings--A Handbook of Surface Engineerings, Blackie & Son Ltd, Glasgow G64 2NZ, 1991): EQU 2AX(g)+H.sub.2.fwdarw.A(s)+2HX(g) (1)
in which AX(g) is the gaseous reactant supplied (for example, fluorides, chlorides, bromides, carbonyls, volatile metallo-organic compounds), A is the material of the resulting surface layer (s), H(H.sub.2) is hydrogen as a carrier and HX is the usually toxic and corrosive waste gas. In this case, the suction flow does not determine the speed-determining process step (and productivity limit), but is used primarily for operating safety. It is therefore also not surprising that, in CVD operations with simultaneously occuring and widely differing surface reaction speeds (the term "reaction kinetics" is avoided here, since it often relates to a reaction mechanism, the speed of which can be influenced by mechanism-independent variables), so-called "additives" are added to the reactants, in order to brake (!) the fastest reaction operation and achieve harmonization of all reaction operations on the corresponding surfaces, that is to say a control of the CVD process. It was thereby possible to achieve an accurate control of the composition and nature of the resulting phases by means of CVD processes. The increase in productivity specific to the CVD process was therefore concentrated on the development of suitable compositions of the react and gases supplied to the reaction (cf. D. C. Boyd, R. T. Haasch, D. R. Mantell, R. K. Schulze, J. F. Evans and W. L. Gladfelter, Chem. Mater. 1 (1989), p. 119.) and has consequently hitherto remained independent of the pumping speed S or of the conveying capacity Q which is applied for the waste-gas suction (!) flow.
This is an important reference point in the overall invention designated above: for the purpose of control (of a process), not to accelerate the fastest process step, or even merely to control it, but, above all things, to restrict it! This specific form of process control to increase productivity is the indispensable precondition for the industrialization of an advanced process and allows a better utilization of its inherent advantages. This maxim is pertinent only to those processes which operate in limited areas. Vapor deposition (irrespective of its form (for example, as (reacted) dust, powder, solid blank, etc.) or of its dimension) is such an area, since the fragmentation of matter (which is the decisive criterion for structural and chemical homogeneity controlling the properties of a material) further than down to the individual atom has hitherto also been pojntless for the manufacture (!) of new materials. In complete contrast to this is the rapid solidification, occuring hitherto, which operates in the micrometer fragmentation range and in which the operational fragmentation range is concentrated on the "cross-over" of the fragmentation medium (for example, in gas and water atomization) or, for example, on the "melt puddle" (in "melt-spinning"). In the case of rapid solidification from the melt, the corresponding increase in productivity remains a linear problem and, in actual fact, can be achieved only extensively, that is to say by lining up many "cross-overs", etc., into a "linear" concept (cf. F. W. Baker, R. L. Kozarek and G. J. Hildeman. Proc. "Second Int. Conf. on Spray Forming", Swansea, September 1315, 1993, edt. J. V. Wood, Woodhead Publishing Ltd, Cambridge CB1 6AH, UK, p. 395. and S. K. Das, D. Raybould, R. L. Bye and C. F. Chang, U.S. Pat. No. 4,718,475, January 1988.) with limited efficiency and inventive depth, thus contributing to the current dilemma of this profession.
For, as is known, it is necessary merely to overcome a particular energy barrier, and it needs no great invention to evaporate an infinite quantity of material. Furthermore, in comparison with the CVD and CVR (chemical vapor reaction) processes, physical vapor deposition processes (PVD) also lack a chemical material conversion reaction, and it therefore also cannot control the productivity of a PVD process. Temperature and potential gradients (that is to say, free convection, diffusion) have hitherto remained the predominant propulsion forces of the conveying operations in physical deposition processes (PVD) (cf. D. S. Rickerby and A. Matthews, Advanced Surface Coatings--A Handbook of Surface Engineerings, Blackie & Son Ltd, Glasgow G64 2NZ, 1991.). Consequently, the degrees of freedom and potentials for in novation of the PVD processes have hitherto remained unused. The PVD problem is not a genuine productivity problem, although it appears to be such at first sight in laboratory practise and from outside. Like the CVD and CVR problem, the PVD problem is primarily a question of quality arising as a result of the difficulty, in the case of high productivity, of also continuing to control concentration and phase selection as well as the homogeneity of these parameters in the product in an energy-efficient way.
2. Description of the Related Art
F. Hehmann, EP-Application 94111991.9, Aug. 1, 1994, and PCT Application PCT/EP95/02882 of Jul. 19, 1995 claimed for the first time a vapor deposition process which is driven by the pumping speed S and of which the conveying capacity ("throughput") Q=q*P (q=e.g. volumetric conveying flow or speed q.sub.v [m.sup.3 /sec]) is controlled by forced convection, that is to say by a pump system which is external (that is to say, located outside the distance x between the vapor source and vapor deposition level (said distance being the shortest and being dependent on the plant and diaphragm design)), and for a given pumping speed, by the more detailed design of a "mass filter", the porous diaphragm Diaphragm* (PD). The Diaphragm* is the main structural part of a controlled increase in productivity for vapor deposition, which is necessary (i) to initiate industrial manufacture of solid structural and functional materials as well as their resulting structural parts from the vapor phase, but also (ii) in order to refine the industrial manufacture of (thin) layers and (iii) surface treatment by (physical and chemical) vapor deposition. The Diaphragm* is a plant structural part which brakes a vapor suction flow driven by an external pump system (cf. CVD process) physically by reservoir formation and thereby makes it possible to achieve new, purely physical forms of control. It has the function of a diaphragm for controlling condensation in suction flow-driven vapor deposition processes, with the proviso that the appropriate gases or vapors experience a (stepped) lowering of the microscopic (that is to say, directly at the outlet of the flow ducts) and macroscopic static pressure (that is to say, the pressure in the vapor and/or deposition chambers separated by this diaphragm) at the interface between the separated chambers.
The Diaphragm* claimed in F. Hehmann, EP-Application 94111991.9, Aug. 1, 1994, and PCT Application PCT/EP95/02882 of Jul. 19, 1995 relates not only to a completely new diaphragm family (pure porous and tubular diaphragm asymetric in x-translation (that is to say, the surface perpendicular and/or the shortest transdiaphragm distance and having a selectivity S.sub.k =1 or near to 1), but to a new diaphragm species as such. All diaphragm families have hitherto been used for the separation (dissociation) of components (i.e. S.sub.k unequal to 1), but then a diaphragm was claimed here which has exactly the opposite purpose: namely, (i) the synthesis of ultrahighly (chemically and also physically) homogeneous alloys and mixtures and (ii) the deposition of ultrahigh-purity materials with maximum homogeneity of grain and phase distribution, purity being brought about by the associated distillation effect during the evaporation operation. Since no chemical separating operations take place in the gas or vapor phase, a different division of the (mono)atomic vapor mass from that of a vapor deposition process without the Diaphragm* occurs. However, herein lies the key to industrial synthesis in the vapor phase. The basic requirement placed on this Diaphragm* is to control sharp overall pressure and temperature gradients over its cross section by component-unspecific mass filtration, that is to say without material separation being carried out, unless expressly identified. Conventional material (and heat transmission) coefficients therefore play no (or only a subordinate) part in characterizing this new diaphragm species.
Since no chemical separating operations occur during transdiaphragm material conveyance, also no conventional osmosis, that is to say chemical potential gradients, can exert a controlling effect on material conveyance. It therefore goes without saying that the conveying operations are governed only by the variables, (under)pressure and temperature, and by a flow force which is imparted to the chamber system of the process as a whole from outside (that is to say, outside the conveying distance between the vapor source and vapor deposition) and which maintains and controls the underpressure system. "Osmotic pressure" transferred to the new vapor deposition process therefore occurs only in the case of a negative temperature gradient, toward which the vapor flow or gas flow must flow and for which the external pump system provides the propulsion force under the structural conditions of the Diaphragm* solutions. Since the suction flow conveying capacity Q for a given pumping speed S is controlled by the Diaphragm*, thermal convection is subordinatyed to forced mechanical convection as a control variable and is used merely for fine adjustment in the interdiaphragm chamber region. One of the possible means for implementing the process is the bifurcations (cf. the Second part of the invention) which are fitted in front of (screen mode) or in (depth filter mode) the Diaphragm* and which branch off controlled part flows from the evacuation flow in a turbulence- and/or condensation-minimizing, hence maintenance-friendly way and, return them into the original chamber for the purpose of reservoir formation. In this case, retentivity is expressed by the force of the Diaphragm*, said force being distinguished from the frictional force of a flow resistance which does not allow and/or control any high transdiaphragm state gradients without condensation.
In contrast to this, Sh. Tanaka, Japanese Patent JPA 02,125866, May 14, 1990, claims a throttle system, namely a type of flow resistance, which is to assist assist in controlling a pressure flow which equalizes the density of the vapor trajectories and which is generated by the relatively high saturation vapor pressures of the relatively highly volatile metals Mg and Zn. The specific advantage of the Japanese patent consequently remains restricted to a plant structural part without great diversification depth and therefore to the vapor deposition of alloy systems of the Mg--Zn (and also Mg--Li) type which, for example, play or will play no primary part in corrosion-resistant Mg alloys. Since the vapor pressure curve of Mg and Zn (or Li) are relatively similar, no plant structural parts of fundamentally differing function are required for controlling the resulting elementary pressure vapors. The Japanese patent therefore also permits no process control by the utilization of a productivity and quality increasing vapor suction flow which becomes necessary particularly when components having widely differing and/or low vapor pressures are to be evaporated and deposited. A further disadvanatge of the Japanese patent is that conventional flow resistances of whatever type convert directional flow into turbulences and may make it very difficult to achieve controlled vapor deposition for the manufacture of products.
It is unnecessary, at this juncture, to deal with the situation, widely discussed in the literature, where, without further control of the vapor trajectories, the (physical) vapor depostition rate decreases in thickness from the center of the deposited material toward its sides, depending on the process conditions adopted. It goes without saying that, in the suction flow-driven vapor deposition process, the Diaphragm* provides an outstanding solution for controlling this geometrical inhomogeneity problem. The depth of innovation of the Patent JP-A 02-125866 is therefore very limited. For what is forgotten in most cases is that the absolute thickness t.sub.R of the deposited material decreases with an increasing distance s.sub.DR from the vapor source. This connection follows the relation (cf. D. S. Rickerby and A. Matthews, Advanced Surface Coatings--A Handbook of Surface Engineerings, Blackie & Son Ltd, Glasgow G64 2NZ, 1991): EQU t.sub.R =k(s.sub.DR).sup.-n
in which the coefficient k is determinded primarily by the evaporation rate of the material or materials involved and the exponent n is determined by the remaining conditions of the vapor deposition process. Any form of controlled, hence serious "upscalings" of the (industrial) production of materials from the vapor phase therefore cannot avoid causing the coefficient n to tend as far as possible toward zero or (for k values&lt;1) toward negative values and k (for n=0) to become as high as possible. Thus, as the result of a temperature rise from 2200 to 2400 K, a rise in the deposition rate of yttrium by the factor 5.5 was observed, but, at a constant temperature of, for example 2400 K, the maximum deposition rate at the geometrical deposition center in the case of a distance of 50 cm from the vapor source was not even 10% more than that in the case of a distance of 10 cm (see R. Nimmagadda and R. F. Bunshah, J. Vac. Sci. Technology 8 (6), 1971, pp. VM86-VM94). If only because of the long distances which the Diaphragm* allows for vapor conveyance, a control of the form of the deposited blank becomes possible, not just by controlling the vapor trajectories directly before deposition (cf. F. Hehmann, EP Application 94111991.9, Aug. 1, 1994, and PCT Application PCT/EP95/02882 of Jul. 19, 1995).
The comparison of EP Application 94111991.9 with conventional CVD practise (cf. D. S. Rickerby and A. Matthews, Advanced Surface Coatings--A Handbook of Surface Engineerings, Blackie & Son Ltd, Glasgow G64 2NZ, 1991) is also pertinent: in the EP application, the Diaphragm* is the control medium (structural part) and the suction flow imparts the propulsion force (productivity) for the process, whilst, in conventional CVD and CVR practise, the composition of the reactands is the means for controlling the process, whereas the specific productivity of the CVD process is determined by the diffusion operations in the immediate vicinity of the reaction surface of the boundary layer or by the reaction operations on the respective surface and by its dimensions. In light of this comparison, the productivity claimed by EP Application 94111991.9, that is to say increased a result of the interaction of the suction flow with a porous diaphragm (Diaphragm*), brings about, particularly for a PVD process, an increase in the vapor conveying capacity over unlimited distances and, to that extent, allows a productivity increase in the deposition of the (mechanically) conveyed vapor which, in comparison with the conventional PVD processes, is dominated by (mechanically) directed vapor trajectories, but still does not provide any productivity increase in the specific evaporation conditions themselves.
The Diaphragm* is therefore dedicated to a new philosophy of controlled material conveyance. As a plant structural part, it is distinguished from all previous separating diaphragms, including porous and diffusion diaphragms, but also from the conventional flow resistance. It is associated with a suction flow, since material conveyance must remain undisturbed not only by chemical (that is to say, component) separating operations, but also by physical separating operations, such as in the case of a variation in the physical state (that is to say, condensation, sublimation) before controlled vapor deposition at the deposition level which consists of at least one deposition chamber and/or substrate.
Since, with magnesium, on account of its high vapor pressures p*, it is so easily possible, depending on the evaporation temperature T on the condensed surface, to produce large conveying quantities q.sub.v from the resulting vapor phase and deposit solid parts, it is actually not surprising that the vapor deposition of magnesium and its alloys constitutes a potential starting point for a new direction of development in the processing metal, semiconductor and semimetal industry and in the further-processing ceramic industry. On the contrary, the fact that magnesium "lags behind" as a competitive material and experience accumulated in rapid solidification with Mg alloys must rather be seen as proof (of this starting point) (cf. F. Hehmann, EP Application 94111991.9 , Aug. 1, 1994, and PCT Application PCT/EP95/02882 of Jul. 19, 1995; F. Hehmann and H. Jones, Rapid Solidification of Magnesium Alloys: Recent Developments and Future Avenues, in `Rapid Solidification Technology`, eds. T. S. Sudarshan and T. S. Srivatsan, Technomic Publishing Co., Inc., Lancaster, Basle, 1993, pp. 441-487; G. Neite, K. Kubota, K. Higashi and F. Hehmann, Mg-Based Alloys, in "Structure and Properties of Nonferrous Alloys", ed. K. H. Matucha, Vol. 8 of Encyclopedia "Materials Science and Technology", eds. R. W. Cahn, P. Haasen and E. J. Kramer, VCH Weinheim, P.O. Box 10 11 61, D-6940 Weinheim, RFA, to be published in 1995.
Now, in relation to F. Hehmann, EP Application 94111991.9 , Aug. 1, 1994, and PCT ApplicationPCT/EP95/02882 of Jul. 19, 1995, further configurations, options and details of a controlled vapor deposition with the Diaphragm* as the main structural part for appropriate "upscaling" are developed and claimed and form the plant modules of a future vapor deposition factory with production conditions adaptable to the respective product requirements. With the increasing diversity of couplable plant modules, the diversity of the corresponding production lines, products and production possibilities increases.